1. Field of the Invention
The present invention relates to a mechanical scribing apparatus with controlling force of a scribing cutter for scribing a surface of a work with a scribing tool and, more specifically, to a mechanical scribing apparatus with controlling force of a scribing cutter most suited for scribing thin films of number of cells arranged on a substrate for electrically separating unit cells from each other in the process of fabricating a thin-film solar cell.
2. Description of the Related Art
Recently, there has been developed a thin-film solar cell having a light absorbing layer made of chalcopyrite compound (CIGS (Cu(InGn)Se2) type compound), which possesses an excellent power conversion efficiency and high stability of output characteristic.
FIG. 1 shows a structure of a CIGS thin-film solar cell. It comprises a SLG (soda lime glass) substrate 1 on which a lower molybdenum (Mo) electrode layer (positive electrode) 2, a CIGS-type light absorbing layer 3, a buffer layer 4 of ZnS and a transparent upper electrode layer (negative electrode) 6 of ZnO:A1 are subsequently formed in the described order. In FIG. 1, there is shown a positive side output electrode 7 and a negative side output electrode 8.
In mass production of the thin-film compound semiconductor solar cells, there is used such a modular structure in which a plurality of the above-described unit cell structures are monolithically formed on a single substrate. The unit cells monolithically formed on the substrate therefore must be electrically separated from each others.
In the conventional process, the electrical separation of unit cells can be easily carried out by partially removing thin films between respective cells by laser scribing method (JP H11-312815). However, the laser scribing method may concurrently heat boundaries of respective cells at a very high temperature, resulting in deterioration of characteristics of cells by the effect of heat.
Thus, the separation of thin film solar cells on a single substrate by laser scribing involves a problem of deterioration of performance characteristic of respective cells by the effect of the high heat energy of a laser beam.